The effect of interval from day of administration of bovine somatotropin (bST) to synchronization of ovulation and timed-insemination on conception rate of dairy cows with and without ovarian cysts

The objective of this study is to evaluate the effect of the interval from the day of administration of bovine somatotropin (bST) to the day of initiation of synchronization of ovulation (Day 0 and 7) and timed-insemination (TAI) on conception rate (CR) of dairy cows with and without ovarian cysts, respectively. Lactating dairy cows (n = 359) were divided into two groups. Cows in Group 1 (n = 238, without ovarian cysts) were treated with 100 microg, i.m. GnRH on Day 0; 25 mg, i.m. PGF2a on Day 8. 100 mirog. i.m. GnRH on Day 10; and inseminated 16 h later without detection of estrus. Cows in Group 2 (n = 121, with ovarian cysts) were treated with 100 microg, i.m. GnRH on Day 0; 100 microg, i.m. GnRH on Day 7; 25 mg, i.m. PGF2alpha on Day 14, 100 ug, i.m. GnRH on Day 16; and inseminated 16 h later without detection of estrus. Between 60 and 63 days postpartum, all cows in the herd were given bST every 14 days for the duration of the study. Logistic regression was used to assess the risk of nonpregnancy associated with interval from bST treatment to Day 0 for cows without ovarian cysts. and both Day 0 and 7 for cows with ovarian cysts adjusting for parity and days in milk. The CR for cows in Group 1 was significantly higher when the interval from last treatment with bST to Day 0 was between 1 and 3 days (28%) compared to 4-6 days (14%). In addition, the risk of nonpregnancy was 2.19 times greater in cows 4-6 days after bST treatment compared to 1-3 days after adjusting for parity and days in milk. The CR for cows in Group 2 was not significantly different when the interval from last treatment with bST to both Day 0 and 7 was between 1 and 3, 4 and 6, and 7 and 14 days. In conclusion, the results of this study suggested bST treatment closer to Day 0 had a positive effect on CR of cows without ovarian cysts, but bST treatment closer to both Day 0 and 7 had no effect on CR of cows with ovarian cysts. This was interpreted to mean that bST had a beneficial effect on either, or both, the preovulatory follicle and the oocyte in dairy cows without ovarian cysts, but not in dairy cows with ovarian cysts.

Prostaglandin production in the umbilical and uterine circulations in pregnant sheep at 129-136 days gestation

Prostaglandins circulating in the maternal and foetal blood have been implicated in important physiological systems. These functions include foetal adrenal function, maintenance of patency of the ductus arteriosus, regulation of uterine and umbilical circulations, and labor and delivery type myometrial contractions. The placenta is a major site of prostaglandin production in pregnancy. Limited data are available which combine measurements of veno-arterial differences across the uterine and umbilical circulations with blood flow in these circulations to enable calculation of umbilical-placental and utero-placental production rates for the prostaglandins. In chronically instrumented pregnant ewes, between 129 and 136 days of gestation, prostaglandin F2 alpha(PGF2 alpha), 13, 14 dihydro-15-keto prostaglandin F2 alpha (PGFM), prostaglandin E2 (PGE2) were measured in the maternal carotid artery and uterine vein. Foetal PGE2, and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) (the major metabolite of prostacyclin) were measured in umbilical venous and foetal descending aorta arterial plasma. Umbilical and uterine blood flow were measured using the diffusion-equilibrium technique. Uterine blood flow was 1693 +/- 137 ml.min-1 (mean +/- SEM); uterine production rates were 480 +/- 88 ng.min-1 for PGF2 alpha, 517 +/- 144 ng.min-1 for PGFM, and 165 +/- 27 ng.min-1 for PGE2. Umbilical blood flow was 147 +/- 17 ml.min-1.kg-1 foetal body weight. Umbilical production rates into the foetal circulation were 11 +/- 2 ng.min-1.kg-1 for PGE2 and 6 +/- 2 ng. ng.min-1.kg-1 foetal body weight for PGI2.

Insulin induced fetal hypoglycaemia and fetal and maternal plasma prostaglandin concentrations in sheep in late gestation

Fetal hypoglycaemia consequent on food withdrawal for 48 h in sheep in late pregnancy is accompanied by an increase in fetal PGE2 plasma concentrations and myometrial contractility. To assess the contribution of fetal hypoglycaemia and related cellular glucopenia in the increased production of fetal PGE2 we studied the effect of 48 h insulin infusion to the fetus. Fetal whole blood glucose was lowered from 19 +/- 2 to 9 +/- 1 mg.dl-1. This experimental regimen maintains glucose availability to those fetal cells in which insulin increases glucose uptake. Fetal umbilical venous and femoral arterial PGE2 concentrations and umbilical veno-arterial PGE2 difference were unchanged, but maternal uterine veno-arterial difference for PGFM increased during the insulin induced fetal hypoglycaemia. Myometrial activity was also unchanged. We conclude that the increased fetal PGE concentration previously reported during food withdrawal is due to a deficiency of glucose to specific insulin dependent cells within vascular beds served by the fetal cardiovascular system. In addition, the findings suggest a need for a supply of glucose of fetal origin for cells that are responsible for increased PGFM concentrations in the maternal uteroplacental circulation.

Maintaining fetal normoglycemia prevents the increase in myometrial activity and uterine 13,14-dihydro-15-keto-prostaglandin F2 alpha production during food withdrawal in late pregnancy in the ewe

Food deprivation during pregnancy leads to an increase in maternal and fetal prostaglandin (PG) production and increased uterine contractility. We investigated the effect of maintaining fetal normoglycemia during food withdrawal-induced maternal hypoglycemia on uterine 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) production and myometrial activity in late pregnant sheep. Pregnant sheep were surgically instrumented with fetal and maternal catheters and electromyogram leads under halothane anesthesia. Maternal and fetal blood plasma samples were obtained once a day at 0900 h, 24 h before (baseline sample) and after 48 h of food withdrawal. Food, but not water, was withdrawn from ewes in group I (n = 5). During food withdrawal in group II (n = 5), glucose was infused into a fetal vein to maintain fetal normoglycemia. All data were normalized to the concentration in the baseline sample in each animal as 100%. After 48 h of food withdrawal, maternal whole blood glucose fell by 42.2 +/- 4.4% (mean +/- SEM: group I) and 31.4 +/- 6.2% (group II). These values were not significantly different. Fetal blood glucose fell by 40.4 +/- 5.7% (group I). In group II, fetal blood glucose was maintained in the normal range (99.6 +/- 1.6% of baseline). Maternal uterine electromyogram activity, uterine venous estrone sulfate, and uterine veno-arterial difference in PGFM rose significantly during food withdrawal in group I ewes, but not in group II ewes. Maternal and fetal arterial plasma ACTH and cortisol did not change in group II animals. We conclude that maintenance of fetal normoglycemia during 48 h of food withdrawal in sheep prevents the increase in myometrial activity, maternal plasma estrogens, and uterine PGFM production during food withdrawal in late pregnancy.